Stability analysis of improved confinement discharges: internal transport barriers in Tore Supra and radiative improved mode in TEXTOR
Results of stability analysis are presented for two types of plasma with good confinement: internal transport barriers (ITBs) on Tore Supra and the radiative improved (RI) mode on TEXTOR. The stability analysis has been performed with an electrostatic linear gyrokinetic code, evaluating the growth rates of micro-instabilities. The code developed, KINEZERO, is aimed at systematic microstability analysis. Therefore the trade-off between having perfect quantitative agreement and minimising computation time is made in favour of the latter. In the plasmas analysed, it is found that the onset of the confinement improvement involves a trigger. For the ITB discharges, negative magnetic shear is involved, whereas for the RI discharges, the triggering role is played by the increase of the impurity concentration. Once the improved confinement is triggered, the simultaneous increases of temperature and density gradients imply an increase in both the growth rate and the rotation shearing rate. The rotation shear is found to be high enough to maintain an improved confinement through the stabilization of the large scale modes.
Bibliographic Reference: An article published in: Nuclear Fusion 42 (July 2002), pp. 892-902
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://stacks.iop.org/0029-5515/42/892
Record Number: 200215556 / Last updated on: 2002-11-25
Original language: en
Available languages: en